1. Field of the Invention
This invention relates to a method of manufacturing a semiconductor device, specifically a doping method of doping impurities into a selective growth silicon layer.
2. Description of the Related Art
A selective growth process is utilized as an effective process for separating fine elements and for manufacturing a contact filling (including, for example, a self-aligning contact).
A conventional example utilizing a selective growth process applied to the contact filling technique is described in reference to FIG. 1. An insulating layer 2 having an opening is formed on semiconductor substrate 1. The resultant structure is provided on a susceptor 5 in a reactive furnace 4 (a reactive chamber) for epitaxial growth. For example, by utilizing H.sub.2 as a carrier gas and silicon chloride or hydrogenated silicon as a material gas, and adding HCl gas and doping gas (gaseous compounds containing impurity atoms in reactive gas), a gas growth process is conducted under reduced pressure. Consequently, silicon layer 3 containing impurities is grown in said opening.
In said conventional method, the impurity atoms adhere to the inner surfaces of the reactive furnace 4 and the susceptor 5 during the growth of silicon layer 3. The adhered impurity atoms float again in the next selective growth process, and contaminate the next growing silicon layer Therefore, in order to selectively grow a silicon layer containing P type impurities and a silicon layer containing N type impurities, both a reactive furnace for p type and for N type impurities are needed, which doubles facility costs. Therefore, a technique is desired, to obtain selective growth of silicon layers doped with P type impurities and those doped with N type impurities, by utilizing a single reactive furnace for epitaxial growth.
Although a technique is produced to dope impurities in a selective growth silicon layer by implanting ions therein, this technique adversely suffers from the reciprocal relation that a large implantation dose cannot result in a deep implantation, while a deep implantation cannot result in a large implantation dose. As a result it is very difficult to obtain a selective growth silicon layer, whose impurity concentration and depth are both large, by utilizing an ion implantation process.